Question about lead seam filler

Two questions actually,
I filled my Quarter seams, but didn’t Get quite enough to be able to file it level. Do I try to add more lead to the low spots, or use plastic filler from here?
If plastic, Should I dig some of the lead out, so there is room for plastic on top of the lead all over, or have some plastic, some lead “surface”?

03A03499-9389-4DC2-B41C-942FAAA7458D.jpeg

8286F415-AE52-478B-8FD4-208A3970F16B.jpeg